We designed a randomized, double-blinded controlled study, and a total of 80 patients with brain hypoperfusion syndrome should be finished assessment in two years. The 80 patients with hypoperfusion syndrome were divided into as follows:1) control group, receiving siwu tang placebo 3 g bid continuously two weeks except ordinary treatment; 2) treatment group, receiving siwu tang 3 g bid continuously two weeks except ordinary treatment. The patients were assessed before, and 4 weeks (weeks±3 days) and 12 weeks (12 weeks±3 days) after siwu tang treatment, respectively. Primary outcome measure was cerebral blood flow by using single photon emission computed tomography (SPECT); Second outcome measure included severity of dizziness by using visual analogue scale (VAS); cognitive function by using Mini-Mental Status (MMSE), Cognitive Abilities Screening Instrument (CASI), and Clinical Dementia Rating (CDR); quality of life by using barthel index (BI) and Functional Independent Measure (FIM).